


Oh My God They Wish They Weren't Roommates

by SixthSeason



Category: Undertale (Video Game)
Genre: (One Sided) Enemies To Friends To Lovers, Insufferably slow burn, Nonbinary Protagonist, Other, Roommates, Slow Burn, Tags to be added (it's gonna be a mess), Underfell, Undertale AU
Language: English
Status: In-Progress
Published: 2020-07-29
Updated: 2020-09-20
Packaged: 2021-03-06 00:00:36
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 4,108
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25593937
Author URL: https://archiveofourown.org/users/SixthSeason/pseuds/SixthSeason
Summary: A housing/roommate arrangement was made. A human stays with the skeleton brothers until repairs in their apartment are done, and in return, the brothers they get half a year's rent waived for taking the human in. Now if only Papyrus had told Sans prior, and not the day of the human moving in with them.
Relationships: OC/OC, UF!sans/OC, sans/OC
Comments: 11
Kudos: 17





	1. The Day Of

“Sans. Our new roommate moves in today.”

Sans had barely even made it home from work, stepping into the kitchen to retrieve a snack before he went up to his room to take a nap. However, once Papyrus had said what he said; Sans was wide awake now.

“what?”

“I said our new roommate moves in today.” Papyrus repeated, a bit slower this time.

“what?!” He snapped.

The taller skeleton rolled his eye lights in his sockets. “Have you gone deaf?! I said---”

“i heard what ya fuckin’ said; and i reiterate: what?! what roommate?! we ain’t got a roommate, and we’re not gonna!”

“Who are you to decide that?!” Papyrus bellowed, storming his way over to the breakfast table and pointing a gloved finger centimeters from Sans’ face. Sans leaped up from his seat, jabbing Papyrus in the chest with a finger of his own.

“who are _you_ to decide _that ?!_ ” He shouted back even louder. “what’s the idea?! goin’ behind my back and bringing in a goddamn roommate?! we don’t fuckin’ need one, and i sure as hell don’t want one!! i pay bills, i do my share of th’ chores sometimes--- i pay rent---and ya couldn’t even find the _decency_ to sit down and talk this over with me before ya went out and grabbed some jackass to move in with us!? fuckin’ hell, ya really are such a---”

A clumsy sounding knock came to the door, and Papyrus stood up from where he had been in Sans’ face, making his way over to the door. “Smarten up, windbag. They’re here!!!” He hissed before opening the door. Upon opening the door, there stood three boxes, stacked on top of each other with a pair of brown hands holding the bottom.

“Come in.” Papyrus beckoned. Wordlessly, the stack of boxes moved forward, halting briefly to gently use their knee to prop the boxes in their arms up just a tad higher. Not even a second later, they stumbled, the boxes were fumbled, and fell forward; boxes went flying halfway across the living room, right below Papyrus’ feet, and one nearly fell back into the hallway. The contents exploded as the mystery roommate fell flat on their face.

A loud gasp is their response, and they scrambled to pick up their things, apologizing. 

“My bad. I--uh--- Let me just---I’m really sorry.” They blustered, hastily shoving their belongings back into their box. 

They were far, far shorter than Papyrus’ towering height, but just about a head and a half taller than Sans was. At least, he thought they were. He couldn’t really tell with how they sort of had their spine hunched a little as if trying to make themself even smaller. When he felt a hand brush past his ankle to retrieve a video game controller, Sans sharply looked down. A pair of brown eyes looked over the rim of their glasses at him. When they met Sans’ eyes, they quickly averted their gaze as they moved on. Sans bristled at that for some reason.

Sans watched with a scowl as the human continued to clean, before looking up to Papyrus with his best dirty look. He **had** to be joking.

“Ahem.” Papyrus cleared his throat. “This is Casey. They will be staying with us for the time being.”

“why.” He said it with such disdain, trying to make it clear to both the human and his brother that he still wasn’t okay with this entire arrangement that he apparently **JUST** found out about. The human definitely noticed, and their hands slowed as they continued to gather up their spilled belongings.

“As a part of an agreement with the landlady.” Papyrus explained. “You see, Casey’s apartment had a cave in the ceiling due to shoddy plumbing work from the apartment above. Long story short, it’s a pretty bad predicament. The repair is going to be a hefty and lengthy one. However, the landlady offered to waive the rent of anyone who took Casey in for the time being for as long as the repairs will last.” Papyrus beamed. “So, there you have it.”

The idea of not having to worry about rent for a while was a welcome one. However, Sans was still very much sore about the fact Papyrus couldn’t even sit down and talk this over with Sans. Chances were, he knew how his older brother would feel about it, and that’s why he went ahead with it without prior consultation.

The human had finally finished putting most of their belongings back into the box. Papyrus gave Casey a firm pat on the shoulder, and they flinched. “Come then. I’ll show you where you’re staying.” He plucked up one of the boxes with ease, heading towards the stairs. “Sans! Be a decent roommate and help Casey with that last box!” He called back.

For a moment, Sans looked over at Casey, giving them a nasty glower. They picked up their own box and were across the room in a heartbeat, trailing behind Papyrus. This was such bullshit. Regardless, Sans picked up the box under one arm, grumbling and cursing under his breath as he followed the both of them upstairs. Papyrus stopped in front of Sans’ door, and immediately, Sans dropped the box he was holding to point at Papyrus.

“that’s _it!!!_ i draw the line here! they ain’t stayin’ in my room!!!” He barked, storming over to Papyrus and wedging himself between Casey and Papyrus and blocking the door. “yer room is bigger; put them in yers!!!”

“And go through all that trouble?! The new furniture has already been assembled, brother.”

Sans blinked. New furniture? He turned around, throwing open his room door. His mattress on the floor was gone; his beloved ball of blankets missing, replaced with---

“a bunkbed!? ya off yer fuckin’ rocker!?”

The human winced at Sans’ yelling, but Papyrus seemed thoroughly unbothered.

“Honestly; could you be any more selfish. Be charitable, brother. After all, we’re free of rent for half a year. Now, if you’re done being a stubborn ass---” Without warning, Papyrus set the box inside Sans’ room, placed a hand on Sans’ and Casey’s backs, and shoved them inside. “Better start making friends!” The door closed behind the two quickly, andn Sans could only stare at the door as if he could make it explode just by looking at it. Stars, next time that asshole came around, he was going to thrash him for this entire bullshit arrangement.

Bringing in a stranger, moving his shit around without his permission, not even talking to him as if he wasn’t the one bringing in half the rent---

A quiet voice brought him out of his slightly homicidal thoughts, and he snapped his head towards the human. “what?!” He snapped.. The human flinched again. They took a deep breath and repeated themself.

“It’s your apartment.” They said quietly. “Which bunk do you want?”

“i don’t give a damn. go nuts.” Sans groused before yanking a pillow and blanket off the bottom bunk and storming out of the room, slamming the door behind him. The entire time, he cursed under his breath as he tossed the pillow onto the sofa followed by the blanket. Angrily, he yanked his phone out his pocket and quickly dialed the number to his job. His boss, Rick, answered.

“Clover’s, you got Rick speaking.”

“rick. won’t make it in tomorrow.” Sans said sharply. 

A pause. “Who is this?”

“sans, dumbass.”

“I know. I was joking.” Sans rolled his eyes. “What’s going on?”

“sick.” He said at length. Rick went quiet for a moment or two, but he didn’t press.

“Alright. I’ll see if Hammer can cover your shift. Get well soon.”

“doubt it.” Sans hung up first, tossing his phone onto the floor before throwing himself onto the sofa and glaring at the ceiling. 

Footsteps approached, and the human came down the stairs, wearing dark gray scrubs with a small white embroidered logo on the breast pocket of the shirt. Sans sat up and raised a brow bone. “where the hell’re ya goin’ this late at night?”

“I work at the hospital.” They said. “Overnight shifts.” They put on their shoes, and opened the door, pausing for a second. “I’ll stay out of your way. I’m sorry for the inconveniences of this arrangement.” And with that, they closed the door.

Fuck’s sake.

Now he felt like an ass.


	2. Frickin' Weirdo

Well, Sans _had_ felt like an ass for a moment or two. Until he remembered he was still very much pissed that this entire arrangement was done behind his back, and this human was an accomplice to it all. However, he felt the slightest bit better that they told him they’d stay out of his way. They’d better, if they knew what was good for them. 

And since they worked overnights, that meant he didn’t have to crash on the sofa in his own apartment, and he would have his room back. For the time being, at least. Sans took his blanket and pillow back up to his room, tossed them on the bottom bunk, drew his blackout curtains shut, kicked off his shoes and jacket, and laid himself out, almost immediately falling asleep; exhausted from the day’s annoyances.

**~~~~~~~~~~~~~~~~~~~**

_ Creak. _

_ Creak. _

_ Creeeeeak. _

Sans snapped awake. He lay there in bed, eye sockets now wide open upon hearing the mysterious creaking noise. He didn’t move for a moment; he wanted to be certain he was actually hearing what he was hearing, and it wasn’t some dream filled haze he was just coming out of. And sure enough, the creak came again. Followed by shaky sounding breathing. He bolted up in bed, looking over to see a shadow descending from the top bunk.

A gasp comes from the shadow as he moved,, and it flails, going to the floor with a loud  _ bang! _ Followed by a pained hiss. Sans quickly switched on his lamp to find the human splayed out on the floor, rubbing the back of their head and groping around for their glasses.

“the hell’re ya doin’?!” He barked.

They didn’t answer, quickly grabbing their glasses, putting them back on and practically dashing out the room, closing the door behind them as they did. 

Frickin’ weirdo.

Not even seconds later did his phone alarm go off, alerting him to the fact it was time to get up so he could actually sleep that night. Sans made a loud, disgusted noise. Thanks to the weirdo, he lost about 5 more minutes of precious sleep. Begrudgingly, he got out of bed, threw his jacket and shoes on, and went downstairs, cursing and grumbling the entire way.

“SANS!” Papyrus emerged from the kitchen, holding a bowl and stirring it furiously. “For the millionth time, I’ve told you not to leave your video games running! It’s going to burn the tv screen!”

“what video game?! i ain’t played since the day before yesterday!” He spat, walking past Papyrus and grabbing his water bottle out the fridge.

“You know which one! That one with the screaming marsupial and obnoxious music! Whatever it’s called. By that one company you love so much. Lawless Lobo?”

“naughty dog.”

“Close enough. Anyway, turn it off before I toss it out the window. The music is starting to give me a migraine!” He ordered before heading back into the kitchen. Just like Papyrus to pin the blame on him for every single thing. He went over to the game console, finger hovering over the power button when he glanced up at the screen. Sans blinked, picking up the controller and unpausing the game. He knew this level. He knew this music. This was the same level he’d been struggling to get past for the last week and a half until rage-quitting because those damn shield baddies kept shoving him off the edge once he landed. Judging by the surroundings, this had to be further in the level. He hadn’t gotten this far. Unless--

“‘ey, boss! you’ve been playin’ this game?”

A scoff. “Please. There are much more constructive ways to spend time than sitting in front of a screen for hours on end.”

Then it must have been-- “where’s the human?”

“Which human, Sans? You and I know plenty.”

“the one we live with, smart-ass.”

“Their name is Casey, dumb-ass. And they’re at work. Said something about being called in to help. Speaking of, will you stop screwing around with that video game and hurry up before you’re late for yours?”

“i ain’t goin. i got the night off.” 

“Ah, perfect! Well, I don’t want to be late for mine. Papyrus hurried out of the kitchen, handing Sans the bowl and spoon. “Here. Keep beating until it forms stiff peaks. Put it in the fridge to chill for an hour and forty-four minutes and seven seconds  _ precisely _ . Then once you take it out, chop up a ripe banana, set the slices on top nearly, followed by vanilla wafers. Put the wafers around the rim of the bowl so they’re standing up. Add some whip cream on top for decor. Got it?”

Sans raised a brow bone and looked up at Papyrus, then back down to the bowl. “yeah. sure. whatever.” 

“Don’t louse this up. Or else.” Sans rolled his eyes, not swayed by Papyrus’ threat, simply waving him off and going into the kitchen. Within the next 5 minutes, Papyrus was out the door. The bowl looked stiff enough, Sans thought with a shrug, taking out the spoon and putting the bowl in the fridge. Sans then went over to the TV, switched off the game console, and set it up over to his own console. Last thing he needed was that human saving over one of his saves or screwing up his data.

It had to have been two or three hours into his gaming session when he heard the jingle of keys in the door. Sans glanced at the wall clock. Odd. Papyrus wasn’t due home for another three or four hours. The door slowly opened, and the human crept in, peeking around, and their eyes going wide seeing Sans on the sofa. As was routine, they looked away from him, shut the door, and quickly started heading towards the stairs.

“ey!” He called after them

They paused.

“what’re ya doin’ skulkin’ around like that? ‘s fuckin’ weird.”

They didn’t respond.

“thought ya were at work.”

“I was.” they said, so softly, that Sans had to struggle to hear it. “Got sent home.”

Not that he cared, but-- “why?”

They went silent, still whispering. “Because.” Another pause. “Sorry.” They hurried up the stairs in a heartbeat. Sans could only stare after them, shaking his head and turning his attention back to the TV screen.

_ frickin’ weirdo. _

  
  


**Notes for the Chapter:**

> Why was Papyrus making banana pudding? Let's just say; it's for a very awkward upcoming dinner. Horf horf horf


	3. H20s out the Nose

“--And then she had the _audacity_ ask me to take it back to the chef, after the fact she had eaten most of it!” Papyrus scoffed, angrily using his steak knife to cut through the slab of meat on his plate. “Then she turns around and wants a refund. Not a half refund: a _full_ one. My policy is if you eat more than half of it and you didn’t like it, you wouldn’t keep eating it. Ah! Casey! You’ve run out of vegetables! Would you care for more?” 

Casey looked over at Papyrus and nodded meekly. If they were honest, they would love nothing more to say “no thank you” and excuse themself from the table. Anything to escape the incredibly tense atmosphere around the dinner table. Sans sat across from them, focused on his plate and barely touching anything; pushing the food around with his fork. 

It was clear that the shorter skeleton would most likely never be interested in being cordial or polite to Casey. And forcing him to sit down at a dinner table with them wasn’t helping the fact either. But it was beyond Casey’s control. It had been nearly a week since they moved in with the skeletons, and Sans and Casey hadn’t spoken more than a few words to each other. And those occasions were not by choice.

Evidently Papyrus had gotten fed up with it. So he cornered both Casey and Sans that morning (having studied both of their work schedules) and told them they were going to have dinner together as roommates. Casey wasn’t keen on the idea at all; but they were far too intimidated to say no to Papyrus. They were surprised that Sans was actually sitting at the table, though. They didn’t know how Papyrus was able to convince him; but he was here.

“So I told her to pay and get out, or I will have her charged for theft and trespassing.” Papyrus continued. “She made such a big show about how ‘terrible my customer service is’ and how ‘she’s never coming back again’. Ha! How can you come back with the threat of a trespass?” He snorted, shaking his head. “Typical Carrie.”

“karen.” Sans corrected with a roll of his eye lights.

Papyrus didn't regard Sans' correction. “So, Casey! It occurs to me we hardly know a thing about you!”

At that point, Casey nearly choked on their broccoli, feeling their heart rate pick up. _Oh God; no. Please,_ **_please_ ** _don’t shift this on me!_ They thought in vain. But Papyrus was watching them intently with his best smile. At least--they thought it was a smile. Those red eye lights, scars on his face, and incredibly sharp smile sent them mixed messages.

“Yeah.” They mumbled. “I---don’t talk about myself a lot.”

“Well, we’re going to change that now!” Papyrus paused for a second to take a drink of wine. “If we’re living together; we aren’t going to do so in anonymity, rudeness, and passive-aggressiveness!” Casey heard a _thud_ under the table, and Sans jumped a foot in the air, swearing loudly and rubbing at his leg, shooting Papyrus a dirty look. Another _thud,_ and now it was Papyrus’ turn to jump and glower at Sans as he rubbed his own leg. Casey began to sweat, hoping to change the subject.

“I--well. What do you want to know?” They said, their voice a little louder this time.

The taller skeleton turned his attention back to Casey. “Let’s start with the basics. What do you like to do?”

“Uh. I play video games. I do like to listen to music. I also play music.”

“Interesting! Which instruments do you play?”

“Bass guitar. And I’m learning the drums.”

“Interesting! Sans, looks like you’ve a fellow musician here! My brother here plays the saxophone.” 

At the mention of his name, Sans looked up at Casey. They averted their gaze once again, not wanting to irritate him further. “Which type? Alto?”

“baritone.” 

“Oh. That’s a good sounding saxophone. How long have you been playing?”

He shrugged. “pretty long.”

They nodded, taking a drink of water. Papyrus seemed pleased as he leaned back in his chair. “Sans, you should play for them sometime.” Sans barked out a harsh laugh.

“yeah right. i don’t do sax before the first date.”

Casey couldn’t stop themself. They snorted and laughed at the wrong time, and the water shot up and out their nose. They coughed violently, whacking themself in the chest and trying to get their laughter under control. 

Within a second, they quickly bolted from the dinner table, and ran to the upstairs bathroom, closing the door behind them. Shit, that goddamn pun shouldn't have made them laugh that hard. It wasn't even that good, or funny, but still. It caught them so off guard. So much so that they pretty much shoot water out their nose and mouth. In--front. Of. their. new. roommates. Belatedly, they felt their face heat up as they looked at themself in the mirror, water still streaming from their nose and the corners of their mouth, and soaked into the front of their shirt.

Oh god. 

They screwed that up, didn’t they.

**Notes for the Chapter:**

> Gonna switch between Casey’s POV and Sans’ POV in this fic


	4. Familar Faces (Is that a good thing?)

“Jessica, it’s me, Casey. I was just wondering if you needed some help at the hospital tonight.”

On the other end of the line, Jessica sighed. Casey winced at her annoyed sounding tone and they swore they could hear her eyes roll when she spoke. “No. We’re good.” And she hung up without another word. 

So much for their plan to pick up another shift and get out of the apartment for another night. After the dinner fiasco yesterday night, the environment around the apartment took a turn for the worse. Papyrus walked around with a scowl that just radiated anger, and Sans had been avoiding Casey more so than usual. That was all the confirmation they needed; they really did screw that dinner up by spewing out their water all over themself at Sans’ joke.

They didn’t know how much longer they could bear the fact that they ruined a perfectly good dinner with their abhorrent table manners. They had to get out of there. Find something to do. Anything to keep themselves out of the apartment for the time being. But they dare not leave the sanctuary that was the pile of blankets on the top bunk. They also couldn’t stay up there forever. They also couldn’t go downstairs and face the skeletons, either. Their hands were tied.

What could they do? They were starting to get bored. And hungry. But the thought of facing their roommates hung over them like a dark cloud. Why, oh why did they have to be so afraid of confrontations?

A knock came to the bedroom door, and Casey locked their phone and went dead quiet. The door opened, and footsteps approached.

“hey.” It was Sans. Casey didn’t respond. An irritated grunt is his response before he left the room and closed the door again. They waited until they were certain he was down the stairs before they picked up their phone again. How long would this go on? They sighed quietly, idly going through their phone until it buzzed with an incoming call. When the caller ID scrolled across the screen, they bolted up in bed and answered it on the first ring.

“Hey, puddin’!” Their best friend, Anita greeted in her sing-songy voice.

“Anita, oh my god, am I glad to hear your voice. I need help.”

Immediately, Anita went serious. “What’s going on? Are you okay? Are you hurt? Do you need me to come over? What happened!?” She asked in one breath. “Where are you?”

“I--I can’t say now. I’m okay, I’m not hurt, but I really,  _ really _ need to get out of here for a while. Could you come over?”

“Say no more. Give me about a half hour, okay? Text me your address so I can let the Uber know. Hang in there, Casey. I’m on my way!” She hung up, and Casey sighed in relief.

My _address_. Casey thought dryly. _ Not any more. _

* * *

It was typical for Anita to say she was going to be there in a certain amount of time but to show up earlier than anticipated. She was always like that, especially if it was a friend in need. It was about 20 minutes after their call when Anita sent Casey the text announcing their arrival, and they sent her the apartment number. Not even three minutes later did the doorbell ring, and Casey scrambled down the bunk bed ladder, dashed out the room, lost their balance, and fell down the stairs with a terribly loud noise, landing face first at the bottom step.

They pushed themself up from the floor to see Papyrus sitting at the table, staring slack jawed at Casey, and Sans on the sofa, looking over his shoulder at them, eyes wide, and video game paused.

All the more reason to get out of here, pronto. Quickly getting up from off the floor, they opened the door, and in stepped Anita, immediately enveloping them in a spine crushing hug. “Casey! I’m so sorry it took me so long to get here. The whole ride over, I was so worried about you. What’s the problem? Tell me everything. Do I need to kick someone’s ass? You just give me a name and I’ll--” She trailed off, her hug stopping. She took a step back and looked over at the sofa.

“Sansy?”

Sans blinked. “anita?”

Her mouth open, she looked over at the table. “Matchstick?!”

Papyrus stood up from the table. “Anita?!”

Wasting no time, she all but bolted across the room, catching Papyrus up in a fierce hug and giving an elated squeal, leaving Casey to stand there, their own jaw hanging open.

_ What the hell is going on?! _

**Notes for the Chapter:**

> Uh-oh

**Author's Note:**

> Insufferably slow slow burn fic. Bear with me. This project is for fun, and I'm trying to write without hyper-analyzing or shooting for perfection. If you like it, let me know <3


End file.
